Comparative histological and Histochemical study of the esophagus in two invasive species Acridotheres tristis and Tilapia zillii in Iraq

Abstract

The current study conducted on two invasive species, the common Myna Acridotheres tristis and Tilapia Tilapia zillii in Iraq. The study aims to identify the histological and histochemical aspects of the esophagus in both species. Histological sections showed that the esophagus composed of four tunica: mucosa, submucosa, muscularis and adventia. The lumen of these parts displayed numerous long folds, these folds were lined by non-keratinized stratifies squamous epithelium in A. tristis, while in Tilapia zillii these folds lined by pseudo stratified columnar epithelium. The tunica mucosa showed absence of muscularis mucosa in both species, so the lamina propria was continued with tunica submucosa. In both species, the histochemical sections showed that the submucosal glands with Alcian blue stain contained acidic mucopolysacharrids, meanwhile the sections with PAS stain showed strong neutral secretions within submucosal glands. The middle part of Tilapia esophagus with alcian blue (pH 2.5) stain appeared that the epithelial crypts contained acidic mucopolysacharrids but no reaction within the epithelium, meanwhile with PAS stain showed strong neutral mucopolysacharrids within crypts and weak neutral mucopolysacharrids within epithelium.